PIC16F87X datasheet(55/218 Pages) MICROCHIP

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DS30292D-page 55

PIC16F87X

7.0

TIMER2 MODULE

Timer2 is an 8-bit timer with a prescaler and a

postscaler. It can be used as the PWM time-base for

the PWM mode of the CCP module(s). The TMR2 reg-

ister is readable and writable, and is cleared on any

device RESET.

The input clock (FOSC/4) has a prescale option of 1:1,

1:4,

1:16,

selected

control

bits

T2CKPS1:T2CKPS0 (T2CON<1:0>).

The Timer2 module has an 8-bit period register, PR2.

Timer2 increments from 00h until it matches PR2 and

then resets to 00h on the next increment cycle. PR2 is

a readable and writable register. The PR2 register is

initialized to FFh upon RESET.

The match output of TMR2 goes through a 4-bit

postscaler (which gives a 1:1 to 1:16 scaling inclusive)

to generate a TMR2 interrupt (latched in flag bit

TMR2IF, (PIR1<1>)).

Timer2 can be shut-off by clearing control bit TMR2ON

(T2CON<2>), to minimize power consumption.

Additional information on timer modules is available in

the PIC® MCU Mid-Range Family Reference Manual

(DS33023).

FIGURE 7-1:

TIMER2 BLOCK DIAGRAM

T2CON: TIMER2 CONTROL REGISTER (ADDRESS 12h)

Comparator

TMR2

Sets Flag

TMR2 Reg

Output(1)

RESET

Postscaler

Prescaler

PR2 Reg

FOSC/4

1:1

1:16

1:1, 1:4, 1:16

bit TMR2IF

Note 1: TMR2 register output can be software selected by the

SSP module as a baud clock.

T2OUTPS3:

T2OUTPS0

T2CKPS1:

T2CKPS0

U-0

R/W-0

—

TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON

T2CKPS1 T2CKPS0

bit 7

bit 0

bit 7

Unimplemented: Read as '0'

bit 6-3

TOUTPS3:TOUTPS0: Timer2 Output Postscale Select bits

0000

= 1:1 Postscale

0001

= 1:2 Postscale

0010

= 1:3 Postscale

•

1111

= 1:16 Postscale

bit 2

TMR2ON: Timer2 On bit

= Timer2 is on

= Timer2 is off

bit 1-0

T2CKPS1:T2CKPS0: Timer2 Clock Prescale Select bits

= Prescaler is 1

= Prescaler is 4

= Prescaler is 16

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

’1’ = Bit is set

’0’ = Bit is cleared

x = Bit is unknown

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